Mitral valve disease is the leading cause of death of Cavalier King Charles Spaniels.

A discovery by a cardiac surgeon at Colorado State University refutes the accepted wisdom that mitral valve disease, the top heart disease in dogs, is an inevitable result of aging in pets. Dr. Chris Orton and his research team believe serotonin is driving the disease in dogs and humans.

“Serotonin is made in the brain and in cells in the gut. We previously thought that those were the only places it was made before it is circulated in the blood,” Orton explains, in a statement released by CSU. “But we found the local creation of serotonin in diseased heart valves. We think that drug-induced and naturally occurring heart valve disease share the same mechanism for creating the disease—the production of serotonin. The valve is making serotonin, which causes its own disease.”

The solution? Find a drug that inhibits the production of serotonin in the heart—which is exactly what Orton and his colleagues aim to do next. Why does this matter? Mitral valve disease, also often called mitral valve prolapse in humans, tends to impact smaller breed dogs and usually develops when they are middle aged or older. Chihuahuas, King Charles Spaniels, and other toy and small breeds tend to develop the disease more often than other breeds. According to CSU, of the dogs that develop heart disease, 40 percent develop mitral valve disease, and the disease is the eventual cause of about 70 percent of all heart failure in dogs.

Orton heads up Project CARE at Colorado State. The project focuses on researching the causes of and development of new treatments for mitral valve disease in dogs. The project is supported through grass roots funding. To learn more about the program or to support the research, visit Project CARE.